Magnetic recording media have been used for various purposes in recent years requiring improved electromagnetic conversion characteristics and improved binder compositions.
However, conventional compositions cannot satisfy various competing requirements.
Known binders are composed of cellulose derivatives, vinyl chloride-vinyl acetate copolymers, polyurethane resin, acryl resin and copolymers thereof, vinylidene polymers and copolymers, epoxy resin, phenoxy resin, synthetic rubber and polyester, which are used alone or in combination of two components. Combinations of a polyurethane resin and a vinyl chloride-vinyl acetate copolymer and combinations of a polyurethane resin and nitrocellulose as described in, for example, U.S. Pat. Nos. 3,242,005, 3,630,771 and 4,152,484 are typical examples. However, when using a combination of two components, the adhesive strength and friction coefficient, which are the most fundamental properties of a magnetic recording medium, cannot both be simultaneously maintained at satisfactory levels.
In order to solve the above described problem, magnetic recording media having a three-component binder composition are described in Japanese Patent Publications Nos. 36647/82 and 36648/82. Although these attempts solve the above described problem to some extent, they do not succeed in preventing or reducing deterioration of S/N under conditions of high temperature and high humidity.